Pulmonary Vessel Cross-sectional Area before and after Liver Transplantation: Quantification with Computed Tomography

Rationale and Objectives: Pulmonary vascular complications of liver disease have a substantial impact on morbidity and mortality in patients who undergo liver transplant. The effect of liver transplantation on the pulmonary vasculature in patients without pulmonary vascular disease, however, has not been described. This study was undertaken to characterize the regional effect of liver transplant on the cross-sectional area (CSA) of pulmonary vessels. Materials and Methods: We performed a single-center, retrospective, cohort study of patients who had a liver transplant between 2002 and 2012 and who had chest computed tomography scans within 1 year before and after transplant. Using ImageJ software, we measured the CSA of small pulmonary vessels (0-5mm2) and the total lung CSA to calculate the percent CSA of pulmonary vessels <5mm (%CSA<5) at the level of the aortic arch, carina, and right inferior pulmonary vein (RIPV). Pretransplant and posttransplant, %CSA<5 were compared, and associations of pretransplant %CSA<5 with clinical parameters were measured. Results: There was a significant decrease in %CSA<5 at the level of the RIPV (0.19% [interquartile range IQR, 0.15-0.26] before vs. 0.15% [IQR, 0.12-0.21] after; P=0003), with a median change of -16.2% (IQR, -39.3 to 3.9) posttransplant. Changes at the level of the aortic arch and carina were not significant. Pretransplant RIPV %CSA<5 was not significantly correlated with severity of liver disease or oxygenation but was inversely correlated with percent change in %CSA<5 (r=-0.39; P=0039). Conclusions: This is the first study to describe a significant regional change in the pulmonary vessels of patients without known pulmonary vascular disease who undergo liver transplant.